Field of the Invention
The invention relates to the evaluation of a scale inhibitor, and more particularly to a device and a method for evaluating a scale inhibitor for a circulating cooling water system.
Description of the Related Art
Typical methods for evaluating a scale inhibitor include a static method and a dynamic method.
The static method for evaluating a scale inhibitor includes a deposition method, a bubbling method, a nephelometry method, a critical pH method, a pH displacement method, and a conductance method. A typical method of calcium carbonate deposition includes: preparing a mixed solution including calcium ions, bicarbonate ions, and a scale inhibitor; heating the mixed solution to form scale; measuring calcium ions remained in the mixed solution to evaluate the performance of the scale inhibitor. The higher the calcium ion concentration remains in the mixed solution, the better performance of the scale inhibitor is. The bubbling method includes pumping the air into a prepared test solution for accelerating scale formation, and evaluating the performance of a scale inhibitor by measuring a stable calcium ion concentration of the test solution. A Glass electrode method, the nephelometry method, the conductance method, the pH displacement method, and the critical pH method are capable of reflecting the chelation of the scale inhibitor and the capability of stabilizing calcium ions, but are not capable of reflecting dispersion and lattice distortion of the scale inhibitor. However, in practical working condition of the circulating cooling water system, the scale formation includes crystallization of free calcium ions into calcium carbonate, attachment of the calcium carbonate crystal on a device surface, and a growth period of the calcium carbonate crystal; and the scale formation cannot be reflected by the static methods for evaluating scale inhibitors. In contrast, the dynamic method can effectively reflect the scale formation in the presence of the scale inhibitor.
The dynamic method is to simulate working conditions of practical production in the laboratory, including flow rate, flow pattern, temperature, water, metal material, and heat transfer intensity. The dynamic method is an ideal neutralizing test method. However, the dynamic method is complicate and time consuming (usually longer than ten days); besides, the adapted device is complicated and expensive.
A typical method for evaluating an antiosmosis scale inhibitor includes establishing a dynamic circulating system, adding scale-forming ion solution to the system at intervals, recording parameters during the operation of the system, and evaluating the performance of the scale inhibitor. The method is only applicable to antiosmosis systems, but not able to reflect the condition in circulating cooling water system.